The major goals of this project are to experimentally explore possible biological effects of heavy metals (lead, cadmium, and copper) on the host-parasite relationships of Fasciola hepatica (sheep liver fluke) and its snail intermediate hosts Pseudosuccinea columella (non-target hosts); and to use the information accrued from these biological effects to explore the possibility of ultimately developing biological and other means of control of Fascioliasis. It is hypothesized that the presence or persistence of heavy metals at varying concentrations in the aquatic environment, could possibly relate to the propagation, maintenance, and survival of the non-target F. hepatica and its snail intermediate host. Specifically, the aims of this project are as follows: to study the sublethal effects of each heavy metal on a) ability and inability of exposed snails to support polyembryony of the fluke, b) ontogenetic development and reproductive potential of the snails, c) possible mutagenic action of the heavy metals in causing resistance or refractoriness in the snails, d) metabolism (enzyme activity), protein and amino acid profiles, and e) longevity, viability, survival, and infectivity of miracidia. This project will extrapolate from the results of the aforementioned studies, to explain the possible roles that heavy metals may play in the propagation and maintenance of the liver fluke Fasciola hepatica as well as that of their snail intermediate host.